@Hille Thank you for all the answers and recommendations. I apologize for my long silence, which was due to the fact that the continued investigation made me suspect that the problems were not...

I have installed an Archer NX200 together with a Poynting XPOL-2-5G roof antenna. In the router's admin interface I have enabled external antennas and selected Network Mode 5G/4G/3G. However,...